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arXiv · 2211.09936

Dominance of Bursty over Steady Heating of the 4--8 MK Coronal Plasma in a Solar Active Region: Quantification using Maps of Minimum, Maximum, and Average Brightness

Sanjiv K. Tiwari·Lucy A. Wilkerson·Navdeep K. Panesar·Ronald L. Moore·Amy R. Winebarger
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Abstract

A challenge in characterizing active region (AR) coronal heating is in separating transient (bursty) loop heating from the diffuse background (steady) heating. We present a method of quantifying coronal heating's bursty and steady components in ARs, applying it to FeXVIII (hot94) emission of an AR observed by SDO/AIA. The maximum, minimum, and average brightness values for each pixel, over a 24 hour period, yield a maximum-brightness map, a minimum-brightness map, and an average-brightness map of the AR. Running sets of such three maps come from repeating this process for each time step of running windows of 20, 16, 12, 8, 5, 3, 1 and 0.5 hours. From each running window's set of three maps, we obtain the AR's three corresponding luminosity light curves. We find: (1) The time-averaged ratio of minimum-brightness-map luminosity to average-brightness-map luminosity increases as the time window decreases, and the time-averaged ratio of maximum-brightness-map luminosity to average-brightness-map luminosity decreases as the window decreases. (2) For the 24-hour window, the minimum-brightness map's luminosity is 5% of the average-brightness map's luminosity, indicating that at most 5% of the AR's hot94 luminosity is from heating that is steady for 24 hours. (3) This upper limit on the fraction of the hot94 luminosity from steady heating increases to 33% for the 30-minute running window. This requires that the heating of the 4--8 MK plasma in this AR is mostly in bursts lasting less than 30 minutes: at most a third of the heating is steady for 30 minutes.

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Sanjiv K. Tiwari, Lucy A. Wilkerson, Navdeep K. Panesar, Ronald L. Moore, Amy R. Winebarger. 2022-11-17. Dominance of Bursty over Steady Heating of the 4--8 MK Coronal Plasma in a Solar Active Region: Quantification using Maps of Minimum, Maximum, and Average Brightness. https://doi.org/10.3847/1538-4357%2Faca541

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